Dash for Scottish renewables is creating an ‘economic cuckoo’ which threatens security of Scotland’s power supplies

Scientific Alliance Jack Ponton power chart graphic Feb 2015By Prof. JACK PONTON and JOHN WILLIAMS

By 2020, Scotland will be generating a huge surplus of heavily subsidised renewable electricity that it cannot use, sell or store.

The cost implications of producing this surplus will run into billions of pounds, and experts are now demanding that the Scottish Government confirms how it will deal with this huge green surplus – just as Scotland’s cheapest source of electricity – Longannet coal-fired power station, faces closure.

This crisis has been widely predicted. It is entirely a consequence of reducing Scotland’s ability to balance electricity demand by rapidly increasing the variable supply from wind generated power. Wind power is intermittent, it is not secure, and it cannot be stored in the quantities required.

Given the Scottish Government’s renewable energy policy, the crisis is, ironically, a double one of shortages and (very costly) surpluses. 

At times, there will be a shortage of supply that could lead to power cuts, unless power is imported from England (in 2014, Scotland imported electricity from England on 162 days ).

At others, there will be an excess of production that cannot be used but will have to be paid for by consumers or taxpayers. 


In 2010, Scotland had a secure and balanced electricity supply.

There were two nuclear, two coal and one gas-fired power stations, a suite of hydro electric stations providing dispatchable, ie available on demand, power of about 8.4GW. There was a nominal wind capacity of just over 2.5GW.  The red line shows approximate peak demand of 6GW. Scotland’s electricity needs were safe and secure.

Even the loss of a major power station for maintenance or emergency repairs would not have required import of power from south of the border.


By 2015, a major transformation has taken place: the system is still secure but perhaps only just: the lights are still on – but it is costing more.

Cockenzie coal-fired station had been closed. Although Peterhead gas power station now has a reduced capacity there is still 6.7GW of dispatchable power, comfortably in excess of peak demand but susceptible to a nuclear outage.

The transformation has been in the expansion of wind to 7.1GW nominal capacity. Flexible dispatchable power, ie coal, gas and hydro, totals 4.7GW. (Nuclear cannot be conveniently turned on and off so, although it is dispatchable, it is not flexible.)

When the wind blows hard, there is still conventionally generated power to take off line, and the capacity to export up to 3.3GW via interconnection to England.  In 2010, there was 8.6GW of generating capacity; today there is a theoretical 13.9 GW capacity.

However, potential problems are beginning to emerge. Minimum wind load factors of less than 5% can occur so that wind generation can be lower than 0.35GW. For instance, at 2.30pm on 19 January 2015, UK wind load factor was 2.2%) If low wind generation coincides with a reduction in dispatchable generation, power has to be imported. Indeed, imports of power have been required on 162 days in the last three years.

Conversely, high wind speeds resulting in load factors of more than 80%, have at times of low demand required output reductions from Longannet – now the only major Scottish energy resource that can be turned down relatively easily. This increases the cost of operating the plant, and along with other factors such as carbon taxes has brought its future into question. 

Wind turbines may also need to be shut down to avoid overloading the grid, in which case their operators receive ‘constraint payments’ well in excess of their lost revenue.


What will be the position in 2020? Will Scotland benefit from the green electricity ‘bonanza’?

Or will the renewables’ surplus become an unbearable cost to the Scottish economy?

The 2020 configuration assumes that already consented wind farms totaling 8.68GW will have been built, exceeding the Scottish Government’s ‘100% renewable generation’ by nearly 20%.

It is likely that Longannet will have become unprofitable and will close down.  The two Scottish nuclear plants (owned by the French nationalised operator, EDF) should still be operational.There will be 4.4GW of dispatchable power, 1.6GW below the safe threshold. Although the 15.8GW of wind capacity operating above 10% capacity should cover that for most of the time, when load factors fall below this significant shortfalls will occur.

These will have to be met by importing dispatchable power from England, assuming that adequate capacity does in fact exist there. The 2.07GW of nuclear power should provide reliable base load regardless of the weather.

However, when one of these nuclear plants is off line for scheduled or unscheduled maintenance, Scotland’s security of supply will become entirely dependent upon imports.

This is one aspect of the problem that an unbalanced electricity supply will produce. The other, ironically, is what to do with a surplus of power.

Peak demand is at around 6pm on a week day in winter, and minimum demand is always at night at the weekend in summer. This minimum is about 38% of peak, roughly 2.3GW.  Night-time summer demand for electricity would be almost met by the two Scottish nuclear power stations, neither of which can be turned down easily.

With approximately 15GW of installed wind capacity operating at a realistic maximum of 80% load factor, wind generation could peak at 12GW, nearly all of it surplus to Scotland’s needs. 

Since producers get paid their elevated guaranteed price regardless of whether or not there is demand for the power, this represents a substantial cost to consumers – unless the surplus can be used effectively.

Interconnection capacity to England is to be increased to 6GW (at great cost), but this is only about half of the possible excess. 

The current Scottish Government plan is evidently for Scotland to somehow profit from exporting its surpluses. However, when the wind blows hard here it is usually also blowing hard in England and Europe, and consequently spot power prices hit rock bottom.

As it is extremely unlikely that Scotland’s neighbours would be prepared to pay the premium prices which the wind generators have been guaranteed, the cost of the difference will fall on local consumers.

Renewable energy enthusiasts talk about storing electricity but currently the only available means of large scale storage is pumped hydro.

There are two such schemes in Scotland and two in Wales. These have a storage capacity of only 27GWh, just over three quarters of an hour of UK average demand. The new Coire Glas scheme, approved but awaiting a final investment decision, is the only addition currently proposed. This would have a storage capacity of 30GWh.  Average daily electricity consumption in Scotland is about 100GWh. 

Peak excess production over a very windy 24 hours could be nearly 300GWh but Coire Glas could only handle 0.6GW. To absorb 12GW of excess generation would require at least 20 schemes of this size – but the geography and hydrology of such projects is so restrictive that it is not clear if there are any further suitable sites in the country, let alone 20.

How long will it be before the Scottish Government finally acknowledges the truth: that the blind dash for wind is pointless, it will be hugely expensive, and that degrading even more of Scotland’s landscapes will be futile?

Not only is there no need for any more wind in Scotland’s energy mix but the country’s lack of conventional supply will ensure long-term reliance on the UK and Europe for the safety of Scotland’s electricity supply.

Jack Ponton, FREng

John Williams is Chairman of the Borders Network of Conservation Groups.

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